The present invention relates to a chamber and an installation for drying animal excrement, notably poultry droppings.
On account of their high water content, a large number of techniques for drying poultry droppings have already been proposed, the main aim of which is to obtain a dehydrated and deodorized product, easily usable for subsequent applications. A main application is that of fertilizer.
The simplest method consists of blowing air, inside the rearing buildings, above endless belt conveyors which are disposed under the rearing cages and on to which the poultry excrement falls. However, the air becomes only partially laden with moisture, owing to its rapid passage in contact with the thin layer of droppings spread on the conveyors. In order to obtain better efficiency, it would be necessary to use very large volumes of air and provide turbulence within said air, which is very expensive in terms of energy.
In certain cases, this type of method is used within drying tunnels, outside the rearing buildings. The major drawbacks of this type of installation lie in its size and mechanical complexity.
Document EP-B-0 210 196 describes a method and an installation for drying and conditioning chicken manure. The method comprises a step of microbiological conversion of the manure, which necessitates having to closely monitor all the conversion parameters, in order to be certain of ensuring good drying of the manure. Moreover, the corresponding installation is necessarily complex and expensive.
Document U.S. Pat. No. 2,679,114 relates to equipment and a method for the conversion and composting of manure. The equipment comprises a conveyor which transports the raw manure to the upper part of a silo. The base of the silo is formed from two perforated and convergent partitions between which a channel extends. At the base of the channel there is provided a conveyor disposed in a chute. Above the conveyor there extend two parallel rotary shafts provided with blades. Rotational driving of the shafts causes transfer of some of the manure on to the conveyor.
Air under pressure, possibly laden with moisture, is introduced into the mass of manure, through the lower part of the silo, to provide the conversion thereof. The air circulates backwards with respect to the manure, which contributes towards improving the drying or conversion thereof.
Document DE-A-2723581 concerns a method and an installation for aerobic decomposition of organic solids. The installation comprises equipment for pre-drying the material, a storage chamber and a silo for the treated dry product. This chamber and this silo communicate through their bases with a twin-screw conveyor which produces an intimate mixture of the pre-dried product and the dry product.
This mixture is then transferred into a movable-base decomposition reactor, via a vertical conveyor. The mixture can be selectively directed to a drying tower and the final product is stored in the aforementioned silo.
It should be noted that the movable base, as in the previous document, is composed of an assembly of rotary shafts, the periphery of which is provided with fingers or blades.
This type of movable base permeable to air has serious drawbacks.
This is because, when the dried excrement gathers in the form of lumps resembling lumps of earth, this is a particularly hard material. The driving power for the rotating shafts must be particularly high in order to succeed in breaking up the lumps and make them pass into the gaps located between the fingers or blades of two adjacent shafts. Such an increase in power is expensive in terms of energy.
Furthermore, when the shafts are at rest, that is to say not activated rotationally, the aforementioned gaps inevitably allow filtering of the most fluid fraction of the dried material, which is undesirable.
Finally, there is known through the document WO-A-97/02222 an installation for drying animal excrement, comprising a chamber, the base of which is also movable and permeable.
This base is formed from a number of elements consisting of articulated extrusions, capable of swinging simultaneously in order to enable the flow of a fraction of excrement.
This type of installation is satisfactory as regards operation. However, the swinging manoeuvre requires a considerable consumption of energy.
The present invention aims to overcome these drawbacks.
More precisely, it aims to provide an inexpensive drying installation of simple design, which makes it possible to efficiently dry poultry droppings using a reduced volume of air. It aims to achieve this objective using little energy, while recovering the air used with a high degree of saturation in terms of moisture.
Furthermore, it aims to provide an installation in which the movable base permeable to air does not have the drawbacks described above.
According to a first aspect of the invention, this concerns an installation for drying animal excrement, which is adapted to receive a mixture of fresh excrement and dry excrement, the base thereof being provided for holding the mixture while being permeable to air, this base consisting of an assembly of elements each capable of forming a means of holding excrement and having means which make it possible, periodically, to transfer a fraction of dry excrement out of the chamber and through this base.
It is characterised principally by the fact that said elements consist of two series of horizontal crosspieces organized in two superposed parallel planes, these crosspieces being disposed in such a way that the base has no interruption of continuity in the vertical direction, and by the fact that said transfer means consist of at least one slide movable horizontally between these two planes of crosspieces, the longitudinal movement of this slide, capable of sweeping the whole of the surface of said base from one end to the other, pushing the excrement accumulated on the top of the crosspieces of the lower plane, so that it falls by gravity out of the chamber.
Thus, xe2x80x9cthe permeable basexe2x80x9d has only one single type of moving part, namely the slide or slides. This makes it possible to greatly simplify the structure of the chamber and reduce the consumption of energy devoted to moving the slide.
Furthermore, according to other advantageous and non-limitative characteristics of this installation:
seen from the side, the crosspieces are disposed in staggered rows, the edges of the crosspieces of the upper plane partially overlapping the crosspieces of the lower plane;
the crosspieces of the upper plane are perforated;
the chamber has two slides of rectangular form, the width of which is equal to half that of the base, and these two slides are movable in opposite directions;
the means of activating said slides consist of a first cable which connects their transverse edges directed from one and the same side, this cable passing over a series of pulleys, at least one of which is a driving pulley, and a second cable which connects their transverse edges opposite to the first ones, this cable passing over a series of return pulleys, so that, by activation of the driving pulley, one of the slides moves in one direction, while the second moves in the opposite direction;
they comprise means capable of always placing the two ends of the first cable, respectively attached to the first slide and the second slide, under tension;
it has a carriage movable longitudinally, capable of receiving said mixture and distributing it uniformly over said base;
said carriage bears a series of fingers directed downward, capable of levelling the layer of mixture discharged on said base;
said series of fingers can be retracted at the end of the chamber.
The invention also concerns an installation for drying animal excrement.
It is characterised essentially by the fact that it comprises:
means for mixing fresh excrement with dry excrement;
a drying chamber in accordance with one or other of the aforementioned characteristics;
means of blowing air into said chamber, through said base.